Clinical Characteristics of Human Pulmonary Dirofilariasis in Japan: An Uncommon Differential Diagnosis of a Solitary Pulmonary Nodule.

Human pulmonary dirofilariasis (HPD) is a zoonotic disease caused by Dirofilaria immitis. Most HPD cases are asymptomatic and are either detected during annual health checkups or incidentally identified during the investigation of other diseases, particularly primary or metastatic pulmonary lung cancers. However, the frequency and clinical features of Japanese patients with HPD remain unclear. We analyzed data from the Japanese Medical Abstract Society database and identified 69 cases between 1978 and 2022. The incidence of HPD increased until the 2000s but declined markedly in the 2010s. The incidence is higher in the southwestern region and lower in the northeastern region of Japan. Health checkups are the primary diagnostic opportunities. The Chugoku and Shikoku regions have had high incidence rates per population. The diagnosis of HPD using a noninvasive procedure is typically difficult because of the absence of specific clinical symptoms, and approximately 70% of the cases are detected using video-assisted thoracoscopic surgery. Climate change may increase the incidence of HPD in the northeastern region of Japan, and travel to countries with poor vector control may be a risk factor for HPD transmission. Physicians should consider this parasitic infectious disease when examining patients presenting with solitary lung nodules.

Pulmonary coin lesion caused by Dirofilaria immitis - a report of two cases with a minireview of the literature.

Dirofilariasis is a rare zoonosis, transmitted from infested dogs or other carnivorous animals to humans via mosquitoes. Two male patients with a solitary, peripheral, well-defined, coin-like pulmonary lesion in the right upper lobe were presented. Rapid enlargement of the lesion within a few months suggested malignancy, resulting in surgical removal. Microscopic examination of the resected lung revealed necrotic circumscribed lesions with embolized parasites in the vessels. Both parasites were females of the species Dirofilaria immitis. They represent the first reported cases of pulmonary dirofilariasis in Slovenia. Awareness of this entity is important in the differential diagnosis of pulmonary coin lesions.

Human pulmonary dirofilariasis masquerading as a mass.

Pulmonary dirofilariasis, caused by Dirofilaria immitis, rarely affects humans and is usually asymptomatic, but may present as chest pain, cough, hemoptysis, wheezing, low-grade fever, and malaise. The dead and dying worms obstruct branches of the pulmonary artery, causing infarction and a granulomatous reaction. Coin lesions are apparent on radiography, raising concern of malignancy. Complete surgical excision is the treatment of choice and an anthelmintic can be administered if residual lesions are present or the patient is from an endemic area. We present two cases of pulmonary dirofilariasis presenting as coin lesions in the lung, which were clinically suggestive of malignancy.

A 48-year-old man with a solitary pulmonary nodule.

CASE PRESENTATION: A 48-year-old man with a 75-pack-year history of tobacco use was referred to pulmonary clinic for evaluation of an abnormal chest roentgenograph. He had been followed by his primary physician for bronchitis and nonproductive cough over the past year and was recently treated with a course of antibiotics with no change in symptoms. He had no other medical history, was currently smoking two packs of cigarettes per day, and reported working on the docks in a shipyard for five years. On physical examination, he was afebrile with stable vital signs and 97% oxygen saturation on room air. He was well-developed in no apparent distress. On cardiovascular examination, he was in sinus rhythm without murmurs. Chest examination was clear to auscultation. There was no lymphadenopathy. The abdomen was soft and benign. The extremities were without clubbing, cyanosis, or edema. The rest of the physical examination was unremarkable. LABORATORY DATA: Laboratory data demonstrated a white blood cell count of 7,200/ul with a normal differential. Hemoglobin, platelet count, serum electrolytes, liver associated enzymes and coagulation studies were normal. IMAGING STUDIES: The patient had a chest computed tomography (CT) available for review (Fig. 2). What diagnostic study should be performed next?

Public health aspects of dirofilariasis in the United States.

Coin lesions in the human lung present significant differential diagnostic problems to the physician. There are at least 20 known causes of such lesions, including neoplastic lesions, infectious diseases, and granulomas. The human medical literature contains many misconceptions about the life cycle of Dirofilaria immitis, including the method of entry of the infective-stage larvae and the development of the young adult worm. These misconceptions have obscured the recognition of the clinical presentation of pulmonary dirofilariasis and the potential for D. immitis to lodge in many other areas of the human body besides the lung. Exposure to infective larvae of D. immitis is more common in humans than is currently recognized. Reported cases in humans reflect the prevalence in the canine population in areas of the United States. The veterinary literature provides compelling evidence that D. immitis is a vascular parasite, not an intracardiac one. Its presence in the right ventricle is a post-mortem artifact, because it has never been shown to be there by echocardiography or angiography in a living dog, even though these techniques have demonstrated adult D. immitis in the pulmonary, femoral, and hepatic arteries; posterior vena cava; and right atrium of live dogs. Physicians have taken the name "heartworm" literally, believing that the worm lives in the heart and only after it dies does it embolize to the pulmonary artery. However, the coin lesion is spherical in shape, not pyramidal, as embolic infarcts to the lung in humans are known to be. The coin lesion is an end-stage result of the parasite's death in the vascular bed of the lungs and the stimulation of a pneumonitis followed by granuloma formation. This pneumonitis phase of human pulmonary dirofilariasis is often not recognized by the radiologist because of the way pneumonitis is diagnosed and treated and because the developing nodule is obscured by the lung inflammation. Serologic methods for use in humans are needed for clinical evaluations of patients with pneumonitis living in highly enzootic D. immitis regions. As well, epidemiological surveys are needed to determine the real extent of this zoonotic infection.

Pseudo-tumor of the lung, a rare clinical presentation of dirofilariasis.

INTRODUCTION: Pulmonary dirofilariasis is an uncommon entity. Known as a zoonotic disease it can affect humans as a secondary host. A pseudo-tumor of the lung called "coin" lesion is usually detected while performing a chest X-ray for another reason. OBSERVATION: We present a case of pulmonary dirofilariasis due to Dirofilaria sp. in a 72 year old immunocompetent patient who underwent surgery for suspicion of a neoplasm. DISCUSSION: Human pulmonary dirofilariasis should be evoked in asymptomatic patient from endemic area of canine dirofilariasis presenting with a pseudo tumor of the lung.

Pulmonary dirofilariasis: computed tomography findings and correlation with pathologic features.

OBJECTIVE: The purpose of this study was to describe the computed tomography (CT) and pathologic features of 5 nodules of pulmonary dirofilariasis in 4 patients. METHODS: Four patients with 5 nodules of pathologically confirmed pulmonary dirofilariasis who under went CT were enrolled, and the imaging interpretations were retrospectively compared with the histopathologic characteristics. RESULTS: Three of the 4 patients had a solitary nodule, and the remaining patient had 2 nodules. All the nodules were distributed in the right lower lobe and were attached to the pleura. They were all round or oval in shape and ranged in size from 11 to 22 mm in largest diameter (mean=17 mm). On thinner section CT, the nodules had a well-defined smooth margin with or without a shallow notch; they were connected to the arterial branch and, occasionally, to the venous branch. On contrast-enhanced CT, all the nodules contained a homogeneous low-attenuation area, which corresponded to areas of coagulative necrosis on histopathologic examination. CONCLUSION: Although the CT findings of a pulmonary dirofilariasis nodule are nonspecific, awareness of the findings on contrast-enhanced CT and the pathologic appearance of this rare benign condition may facilitate its differentiation from a malignant nodule.

Immunoglobulin G antibodies against the endosymbionts of filarial nematodes (Wolbachia) in patients with pulmonary dirofilariasis.

The dog parasite Dirofilaria immitis can infect humans. Patients with pulmonary dirofilariasis were tested for immunoglobulin G (IgG) antibodies against the surface protein of Wolbachia, the bacterial endosymbiont of D. immitis. These patients showed significantly higher IgG titers than healthy individuals from areas in which D. immitis was endemic as well as areas in which it was not endemic. Titration of anti-Wolbachia surface protein IgG could become useful for diagnostic applications.

Human pulmonary dirofilariasis: uncommon cause of pulmonary coin-lesion.

Pulmonary dirofilariasis is a rare entity caused by Dirofilaria, a dog worm that is transmitted to humans by mosquitoes. The filarial nematode enters the subcutaneous tissue, travels to the right ventricle, dies and then embolizes the pulmonary vessels causing a small pulmonary infarction, which subsequently appears as a solitary nodule. Although these nodules are usually identified incidentally by chest radiography in asymptomatic patients, the lesion is generally presumed to be neoplastic. Diagnosis is made by surgical excision. Awareness of this benign entity is important in the differential diagnosis of pulmonary coin-lesions.

A nodular pulmonary lesion due to Linguatula serrata in an HIV-positive man.

A coin-shaped pulmonary lesion was accidentally detected in a 42-year-old, HIV-seropositive man residing in Bari (Apulia, Southern Italy) during a routine X-ray examination. A lung cancer was suspected, obliging physicians to investigate surgically. After thoracotomy a lung nodule, 1.8 cm in diameter, was excised and submitted for histological examination. Histological analysis revealed a nodular infarctual lesion containing a larva of Pentastomida. Despite the poor state of preservation of the parasite it was possible to recognise some morphological characteristics which enabled the parasite to be identified as Linguatula serrata (Pentastomida, Porocephalida). This is the first case reported in Europe in the lung in a living man due to this parasite, the few others occurring in autopsy reports. No evident correlations were found in the present case between HIV-seropositivity and the development of the parasitosis. The importance of lung nodules caused by metazoan invertebrates is emphasised: even though they are rare in man, they are regularly mistaken for cancer at X-ray examination.

Pulmonary dirofilariasis.

BACKGROUND: Pulmonary dirofilariasis is a rare entity caused by Dirofilaria immitis, the dog heartworm that is transmitted to humans by mosquitos. This filarial nematode enters the subcutaneous tissue, travels to the right ventricle where it dies, and then embolizes the pulmonary vasculature, causing a small pulmonary infarction, which subsequently appears as a solitary nodule. Although these nodules are usually identified incidentally by chest radiography in asymptomatic patients, the lesion is generally presumed to be neoplastic. Diagnosis is made by surgical excision. METHODS: We reviewed the pathology reports at Memorial Medical Center, Savannah, GA since 1990. RESULTS: There have been approximately 150 cases reported in the literature worldwide. We found 4 patients with pulmonary dirofilariasis diagnosed at our hospital since 1992. A review of the pathogenesis of the disease and clinical manifestations, diagnosis, and treatment of this entity are presented. CONCLUSIONS: Pulmonary dirofilariasis is a benign condition, transmitted by mosquitos to humans that results in peripheral pulmonary nodules. Awareness of this entity is important in the differential diagnosis of pulmonary coin lesions.

Paragonimiasis westermani presenting as an asymptomatic nodular lesion in the lung: report of a case.

A 57-year-old man with a history of having consumed fresh-water crab 8 months previously presented with a solitary mass lesion in the left lung without any symptoms. Since neoplastic disease could not be ruled out, an open biopsy was performed, and histological examination confirmed a definite diagnosis of paragonimiasis. A high level of the anti-Paragonimus westermani antibody was detected in the sera of the patient, but this level decreased substantially 3 months after chemotherapy with bithionol.

Human pulmonary dirofilariasis: analysis of 24 cases from São Paulo, Brazil.

STUDY OBJECTIVE: To present the clinical, radiologic, and pathologic aspects of 24 cases of human pulmonary dirofilariasis (HPD) from São Paulo, Brazil. DESIGN: Retrospective study of 24 patients with a confirmed diagnosis of HPD over a 14-year period (from February 1982 to June 1996). SETTING: Thoracic Surgery and Pulmonary Division, University of São Paulo and Hospital Albert Einstein, São Paulo, Brazil. RESULTS: Seventeen patients were male (70.1%) and seven were female (29.9%). Their mean age was 51.4 years. Fifty-four percent of the patients were asymptomatic and 75% had a well-circumscribed noncalcified peripheral subpleural pulmonary nodule on the chest radiograph and thoracic CT scan, located preferentially in the lower lobes. The diagnosis was made after thoracotomy and wedge resections in 16 patients, by videothoracoscopy in six, after a pleural biopsy in one, and after necropsy in one. The pathologic examination of all the nodules revealed a central zone of necrosis, surrounded by a narrow granulomatous zone and peripherally by fibrous tissue. Pulmonary vessels exhibit varying degrees of endarteritis. In all cases, a dead worm, usually necrotic and fragmented, was found. CONCLUSIONS: A subpleural, noncalcified pulmonary nodule in the appropriate clinical and epidemiologic setting should alert the clinician, radiologist, or pathologist to the possibility of Dirofilaria. HPD should be considered in the differential diagnosis of pulmonary nodules.